I recently took delivery of a Woo Audio WA2 amplifier. I am enjoying it immensely (full review in the pipelines) and although it is still running in - Jack recommended +/- 200 hours - I am doing some preliminary research into possible tube rolling adventures.

The amp uses a pair of driver tubes, a pair of preamp tubes and a pair of rectifiers, and tube rolling options seem to be as follows:

Power: 6080(WA/WB/WC), 5998/5998A, 7236, 6AS7G/6AS7GA

Preamp: 6922/E88CC, 6DJ8/ECC88, 7308

Rectifier: EZ80/6V4

From what I have read and in emails from Woo Audio, I believe that the most significant affect on the sound would come from rolling the power tubes; less so from the preamps tubes and even less so from the rectifiers - would you guys concur?

Also, what would you suggest as a starting point in the tube rolling adventure with this amps - specifically the power tubes? What I would want to achieve is a warm/lush sound, but quite open and extended. That is, not neutral/cold, but also not too euphonic, rolled off or closed in (small soundstage).

Any shared experiences in tube rolling with this amp and/or the above tube types would be most welcome! But of course a caveat - would prefer to start with a reasonable budget ($50-$100) so will be avoiding $200 Tung-Sol 5998s or $400 WE421A's

After reading several of your posts and the posts in the WA2 mod thread, I decided to take the plunge and recently ordered the WA2.

One power tube that is not liked very much here is the 6H13C. It has a warm, lush sound. I like it with Beyers and Grados. The JAN CRC 6AS7G is also one that I personally like. Nice detail, very balanced. Have not tried the 7236, but from what I have read from other threads, it is excellent.

I'm currently using the Tung-Sol 5998, I'm generally happy with them. I heard the Cetron/Tung-Sol 7236 are also very good (more neutral sounding?). As for the Western Electric 421A, I don't think I'll be getting them.

Preamp:

I'm using the Bugle Boy & the Orange Globe. They each have their own strength and weakness, I like them both. My next upgrade will most likely be the PQ or the Tungsram 6922 (supposedly they are similar to the PQ).

Thanks for the tips thus far! I have also been looking at the RCA-CRC 6AS7G (black plate) - apparently quite rounded and warm but not soft at the extremes. The others which come to mind are the Bendix 6080's which I've seen go for around $80-100 for a NOS pair.

Jack suggested that for the full-bodied, warmer signature I should look at the 6080's first, 6AS7G's a close second. He said the 5998's excel at detail and control, though are a lot more neutral (can be cold in the wrong setup).

For preamp tubes I have been eyeing the Tesla E88CC Gold Pins (60's-70's Czech production) which are said to be very good and not that costly. Haven't looked too much into rectifiers (I believe they have the least affect on the WA2's sound).

Thanks Skylab...the astronomic pricing of the WE421A are more an amusement to me than anything else . I've tried to get my hands on some Tung Sol 5998's but they are few and far between; when I have seen them they are usually at around $150-$200 for a NOS pair.

By the way, a tube rolling tip I just got from Jack which should be noted - tubes that have large bases (1/4" larger than the stock GE 6AS7G or Tung Sol 5998) would not fit fully into the socket.

Anyone know if the base diameter is determined by tube type (e.g., all 6080WB's have the same diameter) or is it dependant on manufacturer (e.g., two 6080WB's by different manufactures may have different base diameters)?

Hi there. Yes I have been keeping an eye on that thread. I am particularly interested though in which tubes people have found have the most significant effect on the WA2 (that is - preamp, power or rectifier tubes).

This doesn't answer your question, xenithon about which tube roll has a greater effect, but here's a link to a nice overview of different 6922/6dj8/7302 tubes that work with the WA2 and their characteristic sound. (Joe's Tube Lore)